Javascript snake game

I stumbled upon this Javascript online 2D graphics editor. By using the Tetris game as a source of inspiration I recreated snake

The following code is the most interesting part where the visuals are updated based on the user input. The apples and snake tail are both two dimensional arrays that I believe was the easiest way to store their coordinates.

// drawing of dynamic objects
function draw(fill)
{
    function snakeDraw(c) {
        for(var x = 0; x < snake_block.tail.length; x++)
        {
            pixel(snake_block.tail[x][0], snake_block.tail[x][1], c);
        }
    }
    
    if(fill===0) {
        snakeDraw(bl);
    } else {
        snakeDraw(gr);        
        pixel(snake_block.pos_x, snake_block.pos_y, color(99,199,99));
    }
    for(var a = 0; a < apples.length; a++)
    {
        pixel(apples[a][0], apples[a][1], fill===0?bl:rd);
    }
}

// update of visuals
var time_to_move = 0;
function _move()
{
    time_to_move++;
    if(time_to_move >= move_speed || speedup) {            
        if(collision(snake_block.pos_x + move_dir.dir[0], snake_block.pos_y + move_dir.dir[1]))
        {
            game_over=1;
        }
        else 
        {            
            moves++;
        
            if(moves % 7 === 0 && apples.length < 3)
                 spawnApple();
        
            time_to_move = 0;
            speedup = 0;
        
            snake_block.pos_x += move_dir.dir[0];
            snake_block.pos_y += move_dir.dir[1]; 
            snake_block.tail.unshift([snake_block.pos_x, snake_block.pos_y]);
            i = appleCollision(snake_block.pos_x, snake_block.pos_y);
        
            if(i>-1)
            {
                apples.splice(i,1); 
                score += 1;
                snake_block.size += 1;               
                if(move_speed>5)
                    move_speed -= 1;
            }  else {            
                snake_block.tail.pop();
            }  
        }
    } 
}